The present invention provides a fused ring compound of the following formula I 1wherein each symbol is as defined in the specification, a pharmaceutically acceptable salt thereof, and a therapeutic agent for hepatitis C, which contains this compound. A corrected GPS receiver reference frequency drift then enables faster initialization and stable operation of the position solutions made available to users. Coating properties of the silicone compound become good by mixing this solvent composition and the silicone compound. Units from the full database are pruned to minimize an overall cost associated with using alternative units other than the units in the reduced unit database. The liquid repellency internal additive, such as a fluorochemical or fluoropolymer, is present in amounts from about 0. According to the invention, each video image is memorised with a resolution proportional to the weighting factor associated with said video image in order to reduce the memory space necessary for the storage of images and reduce the access time to the memorised images.